class Solution {
public:
    int dx[4]={0,0,1,-1};
    int dy[4]={1,-1,0,0};
    vector<vector<int>> updateMatrix(vector<vector<int>>& mat) {
        int m=mat.size();
        int n=mat[0].size();
        vector<vector<int>> dp(m,vector<int>(n,-1));
        queue<pair<int,int>> q;

        for(int i=0;i<m;++i)
        {
            for(int j=0;j<n;++j)
            {
                if(mat[i][j]==0)
                {
                    dp[i][j]=0;
                    q.push({i,j});
                }
            }
        }
        
        while(q.size())
        {
            auto [x,y]=q.front();
            q.pop();
            for(int i=0;i<4;++i)
            {
                int a=x+dx[i];
                int b=y+dy[i];
                if(a>=0&&a<m&&b>=0&&b<n
                &&dp[a][b]==-1)
                {
                    dp[a][b]=dp[x][y]+1;
                    q.push({a,b});
                }
            }
        }
        return dp;
    }
};
